The office telephone is the primary point of contact of most business people. Typically, corporations invest significantly in their office telephone infrastructure, including the considerable costs of constructing and maintaining a traditional hardwired telephone infrastructure at each enterprise location. In addition, corporations typically invest in a private branch exchange (PBX) network and its associated services, including voice mail, paging and unified messaging systems. Further, most corporations have negotiated contracts with their telephone carriers (e.g., local and long distance carriers) to ensure they obtain the lowest possible rates for calls placed via their corporate network. However, because the corporate workforce is becoming increasingly mobile, more business people are using wireless telephones to conduct their business when they are out of the office. This has resulted in corporations spending a larger portion of their telecommunications budget on wireless communications, with far less favorable negotiated rates than the rates of their corporate network. In addition, wireless communication systems often lack the enhanced conveniences (e.g., interoffice voice mail, direct extension dialing, etc.) that corporate users have come to expect in the office environment and for which most of the costs may have already been paid (e.g., the PBX network).
A solution to the aforementioned problems would be to assign to employees wireless telephony devices (e.g., wireless telephones or pagers) able to access the office telephone system as though they were conventional desktop telephones hardwired to the company's PBX. It is desirable to incorporate wireless devices into the PBX network so that users may place and receive telephone calls using the office PBX telephone system whether they are at their desks or at a remote location (e.g., away from their desks, out of the office, etc.). This would allow the enhanced conveniences of today's PBX networks (e.g., interoffice voice mail, direct extension dialing, etc.) to be available on wireless devices—a feature which is needed in today's society.
There have been recent attempts to incorporate wireless telephones into PBX networks. One system provided by Ericsson, requires the creation of a mini-cellular network within the confines of the enterprise. A cellular switching unit, unique wireless telephones and an auxiliary server are required to route inbound telephone calls to a wireless handset serving as a remote office telephone.
An in-building wireless system has been proposed by Nortel Networks. This system requires the wiring of pico-cells throughout the enterprise's building. The system routes inbound telephone calls to specialized wireless telephones serving as additional office PBX telephones. The wireless telephones cannot be used as conventional standard wireless telephones until they leave the premises.
These systems allow use of a wireless telephone as an office telephone, but they are not without their shortcomings. For example, each system requires specialized cellular equipment and wireless handsets. Moreover, the systems only use the wireless telephones for inbound telephone calls. In addition, these systems cannot use the wireless telephone as a conventional wireless telephone (i.e., not part of the enterprise's PBX network) within the building.